done!

The vihuela de arco is finished!

Fitted a slightly curved bridge, strings, frets (10) and tuned the instrument to
C (1.60mm) F (1.40mm) A (1.00mm) d (0.80mm) g (0.60mm)

Yet, the most challenging part is still to come.
What to do with it?
Most obvious at the moment seems to play chords (over 3, 4 or 5 strings) acompanying melody instruments or voice. If the 'viol' tuning is the most appropriate I haven't yet found out. It might be useful to try other tunings (open chords...)
So, I don't expect to publish sound samples soon....